Eobeet hadfield



' UNITED- STATES PATENT OFFICE.

ROBERT HADFIELD, OF SHEFFIELD, COUNTY OF YORK, ENGLAND.

SELF-HARDENING MANGANESE STEEL,

SPECIFICATION forming part of Letters Patent No. 333,748, dated January5, 1886. Application filed May 7, 1885. Serial No. 164,678. (Nospecimers.) Patented in England December 6, 1884, No.16,049.

To all whom it may concern:

Be it known that I, ROBERT HADFIELD, a subject of the Queen of GreatBritain, residing at Sheffield, in the county of York, England, haveinvented a certain new and useful Improvement in Self-HardeningManganese Steel, (for which I have applied for Letters Patentin England,and which application has been accepted, and is numbered 16,049, anddated December 6, 1884;) and I do hereby declare that the following is afull, clear, and exact description of the invention, which will enableothers skilled in the art to which it appertains to make and use thesame.

To obtain a self-hardening steel, it has heretofore been consideredabsolutely necessary to use expensive foreign and other high class ironsin conjunction with tungsten or its alloys. The great cost of thematerials, its extreme stiffness, its liability to be spoiled inworking, and its inability to be milled or machined have greatly limitedits use and made it inapplicable for many purposes.

My improvement consists of a self-hardening steel containing from twoand one-half to seven per cent. of manganese. By the use of thispercentage of manganese I am enabled to dispense with the tungsten andthe high-class expensive irons mentioned, and to use in place of thelatter more inexpensive and common pig-iron, sufficiently refined ordecarbonized, or iron or steel scrap, either separately or to gether, orsteel produced by any steel-making process. The manufacture of priorself-hardening steel had to be conducted by the expensive crucibleprocess, and it is one of the advantages of my improved steel that itcan be made by any of the known steel processes. The manganese is addedto the charge under treatment in the form of any of the alloys offerro-manganese used in the manufacture and production of steel, such asferro-manganese, silicon, or spiegel. I use such alloys eitherseparately or together in such proportions as to obtain in the resultantproduct a percentage of manganese varying from two and onehalf (2%) percent. up to about seven (7) per cent.,while, preferably, I keep thecarbonlow. The exact proportions or quantities to be employed of suchalloys are governed and regulated, first, by the percentage of manganesecontained therein; secondly, by the character of the materials undertreatment; and, thirdly, by the quality of the steel required to beproduced, such quality being determined by the purpose or purposes towhich it is to be applied; but I have found that where the maximumdegree of hardness is essential in the resultant product such alloys maybe beneficially used in proportions sufficient to obtain in such producta percentage of manganese varying from two and one-half per cent. up toabout five per cent, while, where a lesser degree of hardness isrequired, I have found that it is beneficial to use such alloys inproportions sufficient to produce in the resultant product a percentageof manganese varying from about five per cent. up to about seven percent.

The alloy or alloys employed are either melted with the materials undertreatment or are added thereto when both are in a state of fusion, andthe resultant product may either be run into molds and shapes as withordinary steel and iron castings, or it may be run into ingots or othershapes and may be subsequently hammered, forged, rolled, or other wisereduced into bars, plates, or other forms, as desired.

By my invention I obtain a self-hardening steel, which, althoughextremely hard when cold, yet works quite mild, and which, when beingreduced, allows of a much higher degree of heat being used thanheretofore without deteriorating from its quality, thus facilitatingworking and effecting a considerable economy. It is also very free fromimpuritiessuch as dirt and slag-owing to the increased purifyingproperties of the manganese when used in the percentages hereinbeforeindicated, and likewise from other defectssuch as honey-combs--while thepresence of silicon does not interfere with its self-hardeni ngproperties.

As an example of manufacture, I add to two thousand pounds ofdecarbonized and desiliconized iron eighty pounds of ferro-manganesecontaining eighty per cent. manganese.

Such improved self-hardening steel may be manufactured by any of thesteel-manufacturing processes.

I preferably use an eighty-per-cent. ferro-manganese and produce aself-hardening steelviz., a hard steel which may be used forcutting-tools without. requiring the usual hardening and temperingoperations of heating and quenching in water-containing at least two andone-half per cent. and less than seven per cent. of manganese, andpreferably as little carbon as .40. In this it is totally different fromthe present practice, as all the se1f-hardening steels now in usecontain a very large amount of carbon, averaging from one to one and ahalf per cent. I practically dispense with carbon, my steel containing,preferably, only about four-tenths per cent.

My improved steel possesses the important characteristic of being easilyworked into sh ape when heated, whereas prior self-hardening steels werenot only difficult to forge into form on account of stiffness, but alsoeasily spoiled and rendered worthless, thus requiring more than ordinarycare at the hands of the operator. Moreover, such prior steel cannot beshaped by machining, tooling, or filing, on ac- ROBERT HADFIELD.Vitnesses:

F. BOWDEN, S. Bowman.

count of its hardness, while by heating my improved steel to a dull redand then plunging it into cold water it is brought to a condition inwhich it can be finished to the required shape by machining, tooling, orfiling. Its hardness may then be restored by heating it to a bright redand allowing it tocool in the air.

The plunging of this steel into water does not produce water-cracking,as would be the case with other self-hardening steels, or by my processof making manganese steel described in Patents Nos. 303,150 and 303,151.

- -What I claim, and desire to secure by Letters Patent of the UnitedStates, is

As a new article of manufacture, self-hardening steel containing fromtwo and one-half up to but not including seven per cent. of manganese.

